Basic science advances have brought forth the possibility of applying novel antibody (Ab) functions for vaccination against HIV-1 infection. The catalytic function, which is the focus of this Program, offers a means for rapid and permanent inactivation of HIV. Three inter-related projects and three Cores are proposed. Projects I and II focus on isolating catalytically efficient and specific gp120-cleaving Abs from the autoimmunue repertoire, which displays a propensity towards increased catalytic Ab synthesis. In Project I, covalently reactive analogs (CRAs) of gp120 will be prepared and studied for the capability to bind germline encoded, serine protease-like peptidase sites in Ab light chains. The CRAs will be applied as selection reagents to isolate the gp120 cleaving Abs found in human lupus using phage display libraries. This strategy is designed to isolate catalytic Abs with the ability to combine high affinity binding of the ground and transition state structures of gp120. Project II aims to enhance the specificity and magnitude of the gp120-cleaving activity found in murine lupus by immunization with gp120 analogs, including a discrete component of the CD4 binding site, and with the CRAs of gp120. The CRA immunizations are anticipated to selectively recruit the germline V genes encoding the serine protease activity, and to permit improvement of the catalytic activity over the course of clonal selection. Project III will study the ability of heavy chains (H chains) of anti-gp120 Abs from patients with AIDS to direct the catalytic activity of light chains (L chains) towards gp120. Hybrid Abs will be constructed by protein chemistry and recombinant DNA methods. In all three projects, the catalytic Abs will be characterized biochemically, i.e., their cleavage and epitope specificities will be determined, and their affinity for gp120 and catalytic rate constants will be measured. The Antibody Cloning Core (Core B) will construct phage display Ab libraries for project I and II, and will purify single chain Fv constructs for the biochemical studies for all three Projects. The HIV neutralizing Core (Core C) will study the ability of Abs generated in Projects I-III to neutralize the infection of T cells and peripheral blood mononuclear cells by HIV-1. Core A will be administer and coordinate the individual Projects and Cores. The four Projects and two scientific Cores are conceptually and practically interconnected. The project and Core Leaders are leaders in their fields, and have established extensive collaborations with one another. Overall, this program project is expected to demonstrate the feasibility of applying the catalytic function of Abs in passive immunotherapy of HIV-1 infection. In addition, the covalently reactive gp120 analogs have the potential to serve as prototypes for vaccines that can elicit catalytic immunity for the purpose of prophylaxis against HIV-1.